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91.
Christian Marchal Junzo Yoshida Sun Yi-Sui 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):65-93
In the first part of this paper [Marchal, Yoshida, Sun Yi-Sui 1985] we have analyzed three-body systems satisfying the condition rkR where k is a suitable constant, r the mutual distance of the two masses of the binary and R the distance between the center of mass of the binary and the third mass.That condition rkR puts limits on the acceleration of the third mass and these limits allow us to determine the corresponding escape velocities.In this second part we look for initial conditions under which the inequality rkR will remain forever satisfied and we develop the corresponding tests of escape and their applications.This leads to a major improvement of the knowledge of the nature of three-body motions especially in the vicinity of triple close approaches.The region of bounded motions is much smaller than was generally expected and numerical computations of particular solutions show that we approach very near to the true limit. 相似文献
92.
To better understand the variation of water quality in the Mekong River, sampling and measurement were scheduled twice a week for about 3 years at Vientiane, followed by basic statistical analysis of the observed data. The frequent measurement revealed detailed characteristics of the water quality variation, which had not been detected by monthly observation in the previous studies. The variation in total ionic content was considered to be governed by dilution of the amount of water. Increases in turbidity could be attributed to physical effects including surface soil erosion and bed material resuspension at the time of discharge increase. Nitrogen concentrations were stably low during the low flow period and abruptly increased in May. After the annual maximum in late May, the nitrate concentration steadily decreased regardless of the remarkable rise in the discharge from mid‐July, whereas the ammonium concentration remained at a similar level until October. It was considered that the first small discernable runoff after the long dry season flushed the accumulated nitrogen in the surface soil and mobilized the nitrogen in the riverbed. The variation in phosphorus concentrations was different from that in nitrogen concentrations. During the high flow period, continual dilutions at discharge peaks and occasional large additions of phosphorus by surface runoff were suggested. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
93.
Hiroshi Yoshida Kouji Nakamura Minoru Omote 《Monthly notices of the Royal Astronomical Society》2005,358(1):39-48
We study the continuous limit of the multiple gravitational lensing theory based on the thin lens approximation. We define a new, light-path dependent angular diameter distance and show that it satisfies the optical scalar equation. The distance provides relations between quantities used in gravitational lensing theory (the convergence, the shear and the twist terms) and those used in scalar optics theory (the rates of expansion, shear and rotation). 相似文献
94.
Taketoshi?KodamaEmail author Tadafumi?Ichikawa Kiyotaka?Hidaka Ken?Furuya 《Journal of Oceanography》2015,71(1):65-75
A continuous flow method for the determination of ammonium concentration in seawater from a nanomolar to a micromolar level is described. To prevent spurious peaks derived from salinity difference, a gas-permeable hydrophobic membrane filter was used to separate the manifold into an outgassing section and an indophenol blue reaction section. The indophenol blue reaction section was adopted for colorimetric analysis and is equipped with a 1-m path length liquid capillary cell and a fiber-optic spectrometer, which is able to record the absorbance at multiple wavelengths. The minimum detection limit at wavelength 630 nm is 5.5 ± 1.8 nM, and the calibration curves are linear to at least 2,000 nM. In addition, the minimum detection limit at wavelength 530 nm was 13 ± 5.3 nM, and linear calibration curves were observed until at least 10,000 nM. The slopes of the calibration curves were similar for standards prepared using filtered seawater and ultrapure water. The ammonium concentration of the ultrapure water was similar to those of ion-exchanged water and unfiltered low-nutrient seawater, but was significantly lower than those of filtered seawater and solutions that contained sodium hydroxide. Therefore, ultrapure water is optimal for both blank and standard preparations because of its stable quality and availability. Given its large concentration range and the use of readily available blanks, this method is suitable for the determination of ammonium concentration and helps our understanding of ammonium dynamics in the ocean. 相似文献
95.
High inorganic phosphate concentration in coral mucus and its utilization by heterotrophic bacteria in a Malaysian coral reef
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Ryota Nakajima Yasuaki Tanaka Teruaki Yoshida Tamami Fujisawa Asami Nakayama Yumi Fuchinoue Bin Haji Ross Othman Tatsuki Toda 《Marine Ecology》2015,36(3):835-841
Inorganic nutrient contents of mucus released by Acropora corals and its utilization by heterotrophic bacteria at several different hour intervals in the coral mucus were investigated at a coral reef in Malaysia. The dissolved inorganic phosphate (DIP) concentration was 135‐fold higher than in the ambient seawater, probably due to inorganic P release from the coral gut cavity. We experimentally confirmed that heterotrophic bacteria rapidly (within 8 h) consumed ca. 80% of the initial concentration of DIP derived from coral mucus. High DIP concentration in coral mucus may enhance heterotrophic bacterial production and associated carbon flow in the microbial loop of reef ecosystems. 相似文献
96.
In a weakly ionized plasma, the evolution of the magnetic field is described by a 'generalized Ohm's law' that includes the Hall effect and the ambipolar diffusion terms. These terms introduce additional spatial and time-scales which play a decisive role in the cascading and the dissipation mechanisms in magnetohydrodynamic turbulence. We determine the Kolmogorov dissipation scales for the viscous, the resistive and the ambipolar dissipation mechanisms. The plasma, depending on its properties and the energy injection rate, may preferentially select one of these dissipation scales, thus determining the shortest spatial scale of the supposedly self-similar spectral distribution of the magnetic field. The results are illustrated taking the partially ionized part of the solar atmosphere as an example. Thus, the shortest spatial scale of the supposedly self-similar spectral distribution of the solar magnetic field is determined by any of the four dissipation scales given by the viscosity, the Spitzer resistivity (electron–ion collisions), the resistivity due to electron–neutral collisions and the ambipolar diffusivity. It is found that the ambipolar diffusion dominates for reasonably large energy injection rate. The robustness of the magnetic helicity in the partially ionized solar atmosphere would facilitate the formation of self-organized vortical structures. 相似文献
97.
98.
Geology and geochemistry of lavas at Nekoma volcano: Implications for origin of Quaternary low-K andesite in the north-eastern Honshu arc, Japan 总被引:4,自引:0,他引:4
Abstract Nekoma volcano forms part of the arc axis volcanic array of the North-eastern Honshu arc, Japan, which is commonly characterized by medium-K lava suites. However, Nekoma is exceptional because many of its lavas are low-K. This anomaly has been a matter of debate. Nekoma was active from 1.1 to 0.35 Ma. The volcano consists of thick andesite flows and domes associated with block and ash flow deposits produced during lava dome formation. A horseshoe-shaped collapse caldera was formed at the summit and small lava domes extruded into the caldera. Stratigraphy, published K–Ar ages, and tephrochronology define three stages of volcanic activity, about 1.1 Ma (Stage 1), 0.8–0.6 Ma (Stage 2) and 0.45–0.35 Ma (Stage 3; post caldera stage). Low-K andesites occur in all stages. Extremely low-K andesite was also associated in Stage 2 and medium-K andesite was dominant in Stage 3. In general, lavas changed from low-K to medium-K after caldera formation. Geochemical study of the Nekoma lavas shows that both low-K and medium-K lavas are isotopically similar and were derived from a common source. Adatara and Azuma volcanoes, which lie close to Nekoma, also have both low-K and medium-K andesites. However, Sr isotope ratios or temporal-spatial variations in K-level lava classification vary between the three centers. Comparisons of K suites and Sr isotope ratios with frontal arc volcanoes in North-east–Honshu suggest source heterogeneity existed in both medium- and low-K suites. The K contents of lavas and their Sr isotopes are not simply related. This requires re-examination of models for chemical variation of andesites in arcs. 相似文献
99.
Hitoshi Onuki Masahide Akasaka Takeyoshi Yoshida Munetomo Nedachi 《Contributions to Mineralogy and Petrology》1982,80(2):183-188
Ti-rich hydroandradite often occurs, though usually as a minor constituent, in serpentinized ultramafic rocks and associated gabbroic rocks of the Sanbagawa metamorphic belt. The chemistry of the host rocks is commonly characterized by undersaturation with SiO2. Two Ti-rich hydroandradites from metasomatized gabbroic rocks of the Shibukawa area have been chemically analysed by the wet method. Mössbauer experiments indicate the presence of Fe3+ and Fe2+ in the octahedral sites of these Ti-rich hydroandradites. Wet chemical analyses for total reducing capacity of the present garnets by two different methods together with Mössbauer data imply the presence of octahedral Ti3+ in their structure. Ti-rich hydroandratites, apart from their hydrous property, have a similar crystal chemistry to natural Ti-rich andradites. Ti-rich hydroandradites were probably formed in rocks with unusual chemical compositions within a P-T region of 300–400° C and 4–7 kb under limited conditions of relatively low oxygen fugacity and low μCO2. 相似文献
100.
Matthew D. Jackson Ann H. Muggeridge Shuji Yoshida Howard D. Johnson 《Mathematical Geology》2003,35(5):499-520
We investigate numerically the effect of sample volume on the effective single-phase permeability of heterolithic tidal sandstones, using three-dimensional models reconstructed directly from large rock specimens measuring 45 × 30 × 15 cm. We find that both individual and averaged effective permeability values vary as a function of sample volume, which indicates that permeability data obtained from core-plugs will not be representative at the scale of a reservoir model grid-block regardless of the number of measurements taken. However, the error introduced by averaged data may be minimized using the appropriate averaging scheme for a given facies type and flow direction. 相似文献